Obesity, defined as excess adiposity for a given body size, results from a chronic imbalance between energy intake and energy expenditure. Body mass index (BMI, kg/m2) is an accepted clinical estimate of being overweight (BMI 25 to 30) and of obesity (BMI>30). A BMI above 30 kg/m2 significantly increases the risk of diabetes, hypertension, dyslipidemias and cardiovascular disease, gallstones, osteoarthritis and certain forms of cancer and reduces life expectancy.
In the vast majority of obese individuals, the cause of the excess adiposity is not immediately apparent. A currently accepted working hypothesis is that obesity is the result of a maladaptation of the innate metabolic response to environmental challenges such as unlimited availability of low cost/energy dense foods and sedentariness (Hill et al., Science 1998; 280:1371). The study of energy intake in free living humans has met with only limited success and definitive experimental evidence that hyperphagia causes most forms of human obesity is lacking. Following the discovery of leptin, the interest in the neurohormnonal regulation of food intake has regained momentum. However, while much knowledge has been gained on the regulation of food intake in rodents and other animal species, the understanding of the neurophysiology of feeding behavior in humans remains extremely limited.
Neuropeptides present in the hypothalamus play a major role in mediating the control of body weight. (Flier, et al., 1998. Cell, 92, 437–440.) Melaninoncentrating hormone (MCH) is a cyclic 19-amino acid neuropeptide synthesized as part of a larger pre-prohormone precursor in the hypothalamus which also encodes neuropeptides NEI and NGE. (Nahon, et al., 1990. Mol. Endocrinol. 4, 632–637.) MCH was first identified in salmon pituitary, and in fish MCH affects melanin aggregation thus affecting skin pigmentation. In trout and in eels MCH has also been shown to be involved in stress induced or CRF-stimulated ACTH release. (Kawauchi, et al., 1983. Nature 305, 321–323.)
In humans two genes encoding MCH have been identified that are expressed in the brain. (Breton, et al., 1993. Mol. Brain Res. 18, 297–310.) In mammals MCH has been localized primarily to neuronal cell bodies of the hypothalamus which are implicated in the control of food intake, including perikarya of the lateral hypothalamus and zona inertia. (Knigge, et al., 1996. Peptides 17, 1063–1073.)
Pharmacological and genetic evidence suggest that the primary mode of MCH action is to promote feeding (orexigenic). MCH mRNA is up-regulated in fasted mice and rats, in the ob/ob mouse and in mice with targeted disruption in the gene for neuropeptide Y (NPY). (Qu, et al., 1996. Nature 380, 243–247, and Erickson, et al., 1996. Nature 381, 415–418.) Injection of MCH centrally intracelebroventricular (ICV) stimulates food intake and MCH antagonizes the hypophagic effects seen with α melanocyte stimulating hormone (αMSH). (Qu, et al., 1996. Nature 380, 243–247.) MCH deficient mice are lean, hypophagic and have increased metabolic rate. (Shimada, et al., 1998. Nature 396, 670–673.)
MCH action is not limited to modulation of food intake as effects on the hypothalamic-pituitary-axis have been reported. (Nahon, 1994. Critical Rev. in Neurobiol. 8, 221–262.) MCH may be involved in the body response to stress as MCH can modulate the stress-induced release of CRF from the hypothalamus and ACTH from the pituitary.
In addition, MCH neuronal systems may be involved in reproductive or maternal function. MCH transcripts and MCH peptide were found within germ cells in testes of adult rats, suggesting that MCH may participate in stem cell renewal and/or differentiation of early spermatocytes (Hervieu et al., 1996). MCH injected directly into the medial preoptic area (MPOA) or ventromedial nucleus (V) stimulated sexual activity in female rats (Gonzalez et al., 1996). In ovariectomized rats primed with estradiol, MCH stimulated luteinizing hormone (LH) release while anti-MCH antiserum inhibited LH release (Gonzalez et al., 1997). The zona incerta, which contains a large population of MCH cell bodies, has previously been identified as a regulatory site for the pre-ovulatory LH surge (MacKenzie et al., 1984). Therefore modulators of MCH receptors may be useful in the prevention and treatment of reproductive function. MCH has been reported to influence release of pituitary hormones including ACTH and oxytocin. Therefore, modulators of MCH receptors may be useful in the prevention and treatment of obesity, Cushing's disease, sexual function, appetite and eating disorders, obesity, diabetes, cardiovascular disease, hypertension, dyslipidemia, myocardial infarction, gall stones, osteoarthritis, certain cancers, AIDS wasting, cachexia, frailty (particularly in the elderly), binge eating disorders including bulimia, anorexia, kidney function, diuresis, reproductive function and sexual function.
Two receptor subtypes have been identified in humans, MCH-1R and MCH-2R. Both receptors, as well as the gene for the MCH peptide, have been mapped to regions previously reported to contain a susceptibility gene for psychiatric disorders. In particular, MCH-1R was mapped to chromosome 22q13.2 (Kolakowski et al. 1996). The possibility of linkage for schizophrenia susceptibility locus in this area was suggested by independent studies from 2 groups (Pulver et al. 1994, Coon et al. 1994). In addition, a more recent study (Stoeber et al. 2000) of samples from patients with periodic catatonia, a clinical subtype of unsystematic schizophrenia suggested possible linkage of the region around 22q13. Human genetics implicates these loci not only for schizophrenia but also for bipolar disorder. The second MCH receptor (MCH-2R) has been mapped to chromosome 6q16.2–16.3 (Sailer et al., 2001). Cao et al. (1997) were the first to report evidence of a schizophrenia susceptibility locus in that area. This initial report was confirmed and extended by other reports (Martinez et al. 1999, Kaufmann et al. 1998, Levinson et al. 2000). Schizophrenia has been recognized as a disorder with profound deficits in information-processing and attentional abnormalities. One of the few possible paradigms available to assess these types of deficits in information processing is sensory gating, a filtering process which can be demonstrated by using a paired auditory stimulus. Miller et al. (1993) examined the effects of ICV administered MCH on the decrease in amplitude of the second of two tone-evoked CNS potentials that can be measured when pairs of identical tones are presented 500 ms apart. They found that MCH application decreased sensory gating in this paradigm. Based on pathogenesis and pathophysiology (reviewed in Lewis and Liebermann (2000)) several brain areas have been implicated in schizophrenia, all of which show high expression for MCH receptors: thalamus, midbrain, nucleus accumbens, temporolimbic, and prefrontal cortices. These studies and findings support the use of MCH receptor modulators in the treatment and prevention of schizophrenia.
Kelsoe et al. (2001) recently reported on a genome survey indicating a possible susceptibility locus for bipolar disorder identified on 22q (Kelsoe et al. 2001). The MCH gene which encodes the MCH pro-peptide was mapped to chromosome 12q23.1. This area has been identified by Morissette et al. (1999) in a genome wide scan for susceptibility loci for bipolar disorder in families in the Province of Quebec. In addition, Ewald et al. (1998) showed significant linkage to chromosome 12q23.1 (maximum lod score 3.37) in Danish families suffering from bipolar affective disorder. In addition, Presse et al. (1997) have shown that lithium, the “gold standard” and most appropriate initial treatment for the depressive phase of bipolar disorder, can alter MCH mRNA levels in NGF-treated PC12 cells by increasing mRNA stability. These studies and findings support the use of MCH receptor modulators in the treatment and prevention of bipolar disorder and depression.
Philippe and colleagues (1999) performed a genome-wide screen for a autism susceptibility gene and found suggestive linkage for the region of chromosome 6q16.2–16.3 (maximum lod score 2.23). This finding supports the use of MCH receptor modulators in the treatment of autism.
In all species studied to date, a major portion of the neurons of the MCH cell group occupies a rather constant location in those areas of the lateral hypothalamus and subthalamus where they lie and may be a part of some of the so-called “extrapyramidal” motor circuits. These involve substantial striato- and pallidofugal pathways involving the thalamus and cerebral cortex, hypothalamic areas, and reciprocal connections to subthalamic nucleus, substantia nigra, and mid-brain centers (Bittencourt et al., 1992). In their location, the MCH cell group may offer a bridge or mechanism for expressing hypothalamic visceral activity with appropriate and coordinated motor activity. Thus, modulators of MCH receptor function may be useful in the treatment and prevention of movement disorders, such as Parkinson's disease, Parkinson-like syndromes and Huntingdon's Chorea in which extrapyramidal circuits are known to be involved.
Human genetic linkage studies have located authentic hMCH loci on chromosome 12 (12q23–24) and the variant hMCH loci on chromosome 5 (5q12–13) (Pedeutour et al., 1994). Locus 12q23–24 coincides with a locus to which autosomal dominant cerebellar ataxia type II (SCA2) has been mapped (Auburger et al., 1992; Twells et al., 1992). This disease comprises neurodegenerative disorders, including an olivopontocerebellar atrophy. Furthermnore, the gene for Darier's disease, has been mapped to locus 12q23–24 (Craddock et al., 1993). Dariers' disease is characterized by abnormalities in keratinocyte adhesion and mental illnesses in some families. In view of the functional and neuroanatomical patterns of the MCH neural system in the rat and human brains, the MCH gene may represent a good candidate for SCA2 or Darier's disease. Therefore, modulators of MCH receptors may be useful in the treatment of mental disorders including manic depression, depression, schizophrenia, mood disorders, delirium, dementia, severe mental retardation, anxiety, stress, cognitive disorders, and dyskinesias including Parkinson's disease, Tourette's syndrome, Huntington's disease, cerebellar ataxia, and seizures.
Further, the gene responsible for chronic or acute forms of spinal muscular atrophies has been assigned to chromosome 5q12–13 using genetic linkage analysis (Melki et al., 1990; Westbrook et al., 1992). Therefore, modulators of MCH receptors may be useful in treating muscular dystrophy and dyskinesias, including Parkinson's disease, Tourette's syndrome, Huntington's disease, cerebellar ataxia, seizures, locomotor disorders, attention deficit disorder (ADD) and substance abuse disorders.
Still further, modulators of MCH receptor binding may also be useful in treating epilepsy. In the PTZ seizure model, injection of MCH prior to seizure induction prevented seizure activity in both rats and guinea pigs, suggesting that MCH-containing neurons may participate in the neural circuitry underlying PTZ-induced seizure (Knigge and Wagner, 1997). MCH has also been observed to affect behavioral correlates of cognitive functions. MCH treatment hastened extinction of the passive avoidance response in rats (McBride et al., 1994), raising the possibility that MCH receptor antagonists may be beneficial for memory storage and/or retention.
A role for MCH in the modulation or perception of pain is supported by the dense innervation of the periaqueductal grey (PAG) by MCH-positive fibers. MCH receptor modulators may be useful as antinociceptives or as analgesics, particularly for the treatment of neuropathic pain.
Finally, MCH may participate in the regulation of fluid intake. ICV infusion of MCH in conscious sheep produced diuretic, natriuretic, and kaliuretic changes in response to increased plasma volume (Parkes, 1996). Together with anatomical data reporting the presence of MCH in fluid regulatory areas of the brain, the results indicate that MCH may be an important peptide involved in the central control of fluid homeostasis in mammals. Therefore, modulators of MCH receptors may be useful in kidney function and diuresis.
PCT publication WO 01/21169 to Takeda discloses MCH antagonists of the structural formula shown below:
and PCT publication WO 01/21577 discloses MCH antagonists of the structural formula below:

U.S. Pat. No. 4,701,459 and EP 0 252 503 disclose 2,3-dihydro-2-oxo-1H-imidazo[4,5-b]quinolinyl amine derivatives of structural formula:
as useful in inhibiting blood platelet aggregation. U.S. Pat. No. 4,013,665 claims antiviral, substituted 1,3-dimethyl-1H-pyrazolo[3,4b]quinolines of structural formula below:
PCT publication WO 99/48492 discloses nociceptin antagonists of the formula below:
PCT publication WO 99/53924 discloses analgesic agent of the formula below:
and PCT publication WO 99/19326 discloses compounds of the formula below:

The compounds of the present invention are modulators of the MCH-1R receptor and are useful in the treatment, prevention and suppression of diseases mediated by the MCH-1R receptor. The invention is concerned with the use of these novel compounds to selectively antagonize the MCH-1R receptor. As such, compounds of the present invention are useful for the treatment or prevention of obesity, diabetes, appetite and eating disorders, cardiovascular disease, hypertension, dyslipidemia, myocardial infarction, gall stones, osteoarthritis, certain cancers, AIDS wasting, cachexia, frailty (particularly in elderly), binge eating disorders including bulimina, anorexia, mental disorders including manic depression, depression, schizophrenia, mood disorders, delirium, dementia, severe mental retardation, anxiety, stress, cognitive disorders, sexual function, reproductive function, kidney function, diuresis, locomotor disorders, attention deficit disorder (ADD), substance abuse disorders and dyskinesias including Parkinson's disease, Parkinson-like syndromes, Tourette's syndrome, Huntington's disease, epilepsy, improving memory function, and spinal muscular atrophy.